A:2HgO △_ 2Hg+O2↑
B:Fe3O4+4CO 高温_ 3Fe+4CO2↑
C:Fe+CuSO4═FeSO4+Cu
D:2NaCl(熔融) 通电_ 2Na+Cl2↑
It will be 20 years since Hong Kong returned to China on July 1,1997.(就划线部分提问)
____ ____years will it be since Hong Kong returned to China on July 1, 1997?
若函数fx=sinωx+cosωxω≠0对任意实数x都有fπ6+x=fπ6-x,则fπ3-πω的值等于( )